Well, first of all, you have some very lofty goals - gaining 20 lbs of muscle and dropping 5% bodyfat? Are you attempting to do this clean?
What are your current ststs? I’d like to see how many pounds of fat you’d have to lose to drop 5% bodyfat. Actually, technically, if you gained 20 lbs of muscle with no concomitant increase in bodyfat, right there you’d have a decrease in your actual bodyfat percentage.
Either way, I’ll second Pat’s comments. I don’t think you’re plan to alternate phases on a monthly basis is wise. You may very well end up ‘spinning your wheels’. You’re giving yourself 6 months to do this, which means with 3 months of ‘bulking’, you’d have to be consistently gaining over 1 1/2 lbs of muscle per week - not too likely.
See another thread called “How Much Is Too Much?”. In that thread there are recommendations to systematically increase calories until you start to gain, as opposed to starting an all out bulking phase. I think you’ll be more pleased with that approach.
Oh, and what Patricia said - do some more reading.